The present invention relates to a motor vehicle seat with a backrest, and, more particularly, to a motor vehicle seat with a backrest, containing a spring core and forwardly curved side regions into which there are inserted for the purpose of varying the contour of the backrest inflatable air cushions which, with increasing filling pressure, curve the upholstery of the side regions further forwards with respect to the central region of the backrest.
In a known motor vehicle seat of the type shown in German Patent 3,537,847, air cushions are installed in the upholstery of the side regions of the backrest. The contour of the backrest or the support function of its side regions can be varied only to a relatively limited degree. Moreover, with increasing filling pressure in the air cushions, the surface of the upholstery hardens, as a result of which the seating comfort can be adversely affected.
Furthermore, motor vehicle seats of the type shown in German Patent 3,620,084 provide that the contour of the backrest can be varied. It is possible by mechanical stressing of a metallic support element to vary the support of the upholstery such that the latter is held either in a flat horizontal contour with only slightly precurved side regions, or can adopt under seat loading a contour with more strongly precurved side regions and a rearwardly curved central region. This known seat takes account of the fact that thinner persons require a stronger curve in the central region of the backrest than do wider persons. However, it also required a special configuration of the backrest and, because of the adjusting mechanism, is complicated, trouble-prone and not suitable for an adjustment by compressed air that takes account of safety requirements.
In order to vary the contour of the central region of a backrest, German Offenlegungsschrift 3,522,845 shows an air cushion subdivided into a plurality of chambers between a spring element of flat construction and the upholstery. This measure alone, however, makes it possible to vary essentially only the vertical contour of the backrest, whereas the backrest horizontal contour, in particular of the side regions, remain largely uninfluenced.
In a motor vehicle seat shown in German Patent 3,505,088, a combination of three air cushions serve the purpose of back support in the central region and one air cushion each in the side regions of the back rest serve the purpose of lateral support. A control for the compressed air is provided with a slide via which, among other things, the air cushions for back support can be selected individually or in pairs. In this configuration, as well however, the air cushions are incorporated into the upholstery, as a result of which the contour of the backrest can be varied only to a limited degree.
It is, therefore, an object of the present invention to provide a motor vehicle seat in which the contour of the backrest can be adapted as far as possible to the requirements of the various seat users without the surface hardness of the upholstery being adversely affected.
This object has been achieved according to the present invention in a motor vehicle seat in which a spring core extends with end sections bent slightly forward into the side regions of the backrest, and the air cushions are supported on fixed uprights of the seat and act on the end sections of the spring core on their side facing the uprights. The overall shape of the one-piece spring core is varied by way of these features. Consequently, only the contour of the upholstery is influenced, while the surface hardness thereof is not. The side regions of the backrest are adjusted overall forwards and inwards, so that even relatively thin persons can be effectively supported towards the sides.
The support function of the backrest is further increased, particularly for relatively thin persons, when, according to the present invention, the spring core is constructed such that, with increasing filling pressure in the air cushions, the central region of the spring core curves rearwards or more strongly rearwards.
A currently contemplated embodiment that is deemed optimal with respect to seating comfort and support for as wide as possible a range of seat users combines the foregoing features of with at least one air cushion with settable filling pressure in the central region. This air cushion is preferably inserted between the spring core and a rubberized-hair mat of the upholstery so that even in the central region of the backrest, no surface hardening of the upholstery occurs when the filling pressure in the air cushion or cushions is set to higher values.
The contour of the backrest can be varied even more individually when, according to the present invention, at least two air cushions arranged in the side regions and/or in the central region of the backrest and preferably can be controlled individually. In this arrangement, the air cushions in the side regions of the backrest can be controlled independently of the air cushions in the backrest central region.
In another preferred embodiment of the present invention, four air cushions are arranged above one another in the vertical direction in the central region of the backrest and are controlled such that two adjacent air cushions have the same filling pressure. As a result, in the event of a variation in contour in the central region it is necessary in each case to fill only one air cushion, while another is vented. Due to this type of control and arrangement of four relatively small air cushions, the desired contour can be achieved more rapidly than in the case of an arrangement with three larger air cushions.
The setting of the contour is facilitated when, according to the present invention, a control for that purpose is provided with three pushbuttons for controlling the four air cushions in the central region, a rocker switch for controlling the air cushions in the side regions and a setting element for preferably stepless setting of the filling pressure in the air cushions.
The control can preferably be provided in the seat cushion cover on the entrance side and be retained therein by a locking connection. The setting element, configured as, for example, a setting wheel for the filling pressure can expediently act on a pressure regulator connected to the control.
A space-saving design is produced when, according to another advantageous aspect of the present invention, the air cushions are arranged to overlap one another at least in the unpressurized state.
In yet another embodiment of the present invention, the air cushion or cushions, in particular the air cushions inserted in the central region of the backrest, is/are attached to a flexible carrier mat that is, or can be, removably connected to the spring core. The carrier mat can preferably consist of a textile material, in particular felt material. Such a carrier mat can effectively follow the deformations of the spring core and simultaneously support the air cushion two-dimensionally. The characteristic or the characteristic spring curve of the spring core is maintained virtually unaltered in all directions because the pressure exerted by the air cushions is not transmitted onto the spring, core two-dimensionally, but only locally. Furthermore, owing to the insertion behind the complete covering it is ensured that, upon inflation of the air cushions, the surface of the covering is not hardened or is hardened only to an extent that is not troublesome.
A durable and pressure-proof configuration of the air cushions results when the latter are formed, from welded polyurethane films.
In order to avoid noises at the contact surfaces of adjacent air cushions, intermediate layers made of nonwoven material between the air cushions are provided. These intermediate layers can be formed by the walls of pouches or envelopes which preferably open laterally, surround the air cushions and are removably attached, preferably by the latter, to the carrier mat.